Hey guys I've been fighting an issue trying to get my Racetronix fuel pumps to trigger and while I was probing for power with a multimeter I noticed that when I've got key on the purple fuel level wire has 13.5-14 volts steady thru that wire. My grey wire has a couple volts going thru it when the key turns on. Anybody else run into this issue?? Oh and it's a 91 Z28 btw

 

High side of level sender should have voltage but not full system voltage. There is a 61 Ohm series resistor in the gauge; and another 78 Ohm resistor in the gauge that is parallel to the fuel sender. The voltage at the sender is knocked down quite a bit.

You might have the Racetronix GRAY and PURPLE wires swapped by accident.

The TAN wire at your original firewall bulkhead is the old pump B+. That gets tied to the Racetronix GRAY wire which is the field coil for the new fuel pump relay. The PINK wire at your original firewall bulkhead is the high side of the sender. The colors are confusing as heck because when I see pink I'm thinking that must be the fuel pump B+, but it's not.

 

Cool cool thank you sir! I'll check into it tomorrow. I will say I'm no longer running the stock relay, running Racetronix double pump system I just use the trigger wire off my Dominator ECU to make things happen but nothing is happening. I've been in contact with the guys at Racetronix and tried everything they've suggested but nothing. I just noticed the purple wire with full battery power when I was probing things. I quit for the day before frustration consumed me

 

Honestly, the first thing I did with my Racetronix kit is take the loom off the wire to see how it ticks. That took care of all the confusion for me (and I was a bit confused).

 

Oh boy I'm definitely kicking myself in the nuts for not doing the same! I do like your idea of the grey and purple wires being in the wrong positions. I never even thought of that but it definitely seems like it would be the culprit. Crossed wires sending power to another place that doesn't need it all. I'm wondering if it would be just that easy to swap those wires out on the 7 position connector?? Pretty much willing to try anything at this point

 

No, I wouldn't do that because I'm pretty confident the Racetronix harness is built okay. I was thinking more of your side of the job where you tied in your wires into the Racetronix harness.

Rule of thumb: It's not smart to ***** nilly move wires in an electrical system.
Best to step back and understand what you've got and then do the right thing with confidence.

 

No it's definitely not on my side. The purple wire I'm speaking of isn't the one on the car it's the one on the Racetronix harness that's got full power. The grey wire has a couple volts(Racetronix harness) but their purple wire is fully powered. If I disconnect their stuff and probe it again no power on my purple wire only on the grey. Connect it back up and there's power being back fed thru their stuff down the purple wire going to the level sender gauge. It's hard to explain without pictures

 

Wire colors I referenced were for single pump harness. Maybe wire colors are different for the dual pump harness. Maybe dig up a schematic somewhere so we can all be talking around the same thing.

 

I'd love to but there's none of that with the double pump stuff. The positive side of the relay coils are powered via the gray wire that splits off into both relays (terminal 86). This gray wire gets power from the factory fuel pump circuit. The factory computer (ECM/PCM), relays, wiring etc. must be working properly if our harness is to work. Keep in mind that the factory computer only fires up the fuel pump circuit for a few seconds via a relay when the key is first put into the IGN position to prime the pumps and build fuel pressure in the lines. After that the computer must see a RPM signal to continually power the fuel pump circuit.

The negative side of the relay coils (terminal 85) are powered via the small red and small blue wires which run to the ground control loop connectors at the front of our harness. When a ground jumper is plugged in, the relay on that circuit will have ground all the time and therefore will turn on when +12V is supplied via the gray wire / factory fuel pump circuit. If you unplug a ground jumper and plug in the pressure switch in its place (using the HIH harness), ground will only be supplied when the set pressure is reached and the pressure switch closes the circuit providing ground to the relay.

Battery power routes through the fuse holders to the common terminal (30) on each relay. When the relay is powered on it closes its contact to the normally open terminal 87 which is routed to the pumps via the 7-position MP280 circular connector, intermediate double pump harness (IDPH) and in-tank harness (DP-ITWH) on either the thick red or blue wire.

The in-tank harness (DP-ITWH) has the pump grounds (negative -) tied together on a 1/4" ring terminal. The brass screw (supplied) is used as a grounding stud that is installed through a 1/4" hole which you must install into the top of the hanger by drilling a clean properly-positioned 1/4" hole. The brass screw is inserted from the underside of the hanger hat with the in-tank wiring harness (DP-ITWH) pump ground ring terminal on it. A brass nut is placed on the top side of the screw along with some super glue on the underside (supplied in kit) to help seal the hole. The IDPH harness which plugs into the yellow bulkhead connector on top of the hanger (BCA-4W) has a grounding ring terminal wire beside it. This is placed on the brass screw and secured using the remaining brass washers and nuts.

The BCA-4W must be installed/oriented properly. The locking tab on the retaining clip points away from the topside (atmosphere side) connector port. There are four terminal designations on top of the bulkhead connector in the center E, B, C and D. These must match up to the terminal designations on the in-tank wiring harness connector (vapor-side). If they do not the pumps will not turn on because the terminals will be 180 out. Red and blue are pump power +, black wires are all grounds and violet/purple is for the level sensor signal.

 

That's a very good explanation, thank you. Did you check voltage across the contacts of your stock relay to make sure it's doing its job?

Those stock relays are awful. I got rid of mine and wired the Holley ECU to the tan wire through C100 connector.

 

I'm not using the stock relay for the fuel pump anymore. I'm only using the trigger wire off my Holley harness to trigger the Rx relays. My bulkhead connector out back is corroded and power wasn't going thru so I made a new connector and tied the grey, purple and black wires to that new connector which plugs into the Rx stuff. Let me get on a computer and I'll upload some pics

 

Top view of BCA-4W connector with harness grounds and pump grounds tied in on bottom side

Back view

Side showing orientation of 4 way and in-tank harness with pump ground. connector and in-tank harness match up with each other

ground loops to supply power to each pump separately. Or use a hobbs switch

Fuses new and not popped

Solid battery connection also have that thin ground wire grounded on the coil brackets

Power at the grey wire thru the Rx harness at the round 7 position connector. Power was also the same reading directly from the trigger wire off the Holley harness KOEO

Hit all connections with a multimeter, no power at Red or Blue which is power for pumps.

This is what I see going thru that purple wire KOEO

 

Does the power on the purple wire stay on the whole time during KOEO, and no power what so ever when keyed off? Or, does the power on the purple eventually go off (like the trigger of the prime)? Also, you mentioned that your trigger wire (from ECU) shows 1.63 KOEO. Does that eventually go to zero, stays the same no matter how long (with KOEO) and making sure to check before the initial prime signal has expired? What is your prime signal set at on the Dominator? There was a setting in my HP for amount of time to prime in seconds, can't remember or not if there was a possibility of it being set to zero though, but I would definitely check.

 

I suggest taking all your voltage measurements relative to chassis, not other terminals. That way everything will be relative to a common plane. It might give you more insight.

Is that really 16.3V or did you change scaling on the readout? Seems suspicious the two readings are same numbers and only off by a decimal place.

 

I'll have to recheck in the morning but yes I'm pretty sure the purple wire stays on the whole time KOEO and then back to zero keyed off. Again I'll recheck in the morning. My time for prime in my ECU is set at 4 secs and holds the 1.63v and it'll eventually go back to zero

 

The battery on my on multimeter was dying I gotta pickup a new battery tomorrow. I'll be going thru everything tomorrow too as long as the weather isn't shitty

 

Got it figured out Yay!!! I unplugged the Racetronix crap and plugged back into the factory stuff and boom pump fired right up, but I've also got a dead pump so I ordered another pump. So the guy building this harness must've been smoking too much dope that day.

 

Glad you got it figured out.

Yeah, my next reply was pretty much going to be that you seem like a really smart guy and I don't think I can actually help you beyond what you can already figure out on your own.

 

Yea I was back n forth with Rx and they kept saying it was definitely on my end, but my job literally ended at the bulkhead above the diff. I made sure everything had what it was looking for and so finally I just bought a 4 way connector to plug into the BCA-4W in the fuel sender and bam pump fired up. I even emailed them about what I figured out and again they came back with it being on my end. Oh well it happens I guess. Now I just need that pump to get here and I can finally move past this whole thing

 

Doesn't surprise me. I've spoken to the owner of Racetronix a few times. Really smart guy, very poor listener. Can be very difficult and close minded. Sees things in absolutes and can't comprehend the enormous gray field in between.

They do usually make very good product though. Like I said, he's a really smart guy.

 

Absolutely agree with that! They make awesome products and lemons happen to make it thru the line without being caught sometimes, it happens but the guy just can't believe that it does actually happen. That's what I was trying to get across to him yesterday on their forum but he wasn't having any of it

 

I have never used or seen (first hand) any of the Racetronix Products...

Some of the individual Parts look great.
I have no idea about any of the Wiring-Harness Products; I would prefer to see schematics of stripped down Versions before commenting.

...some of the "Kits" confuse me in terms of Connectors used; and I am not a fan.

 

Definitely. Their stuff is great! I think a metric **** ton of confusion would be alleviated if they just made a simple wiring schematic that can be downloaded. When I talked to the guy he said the issue was on my side and I was overlooking something and all their harnesses are 100% computer tested before heading out the door.

It's not rocket science and when everything is connected as it should be and nothing works but unplug their stuff go back into the factory stuff and suddenly everything works as it should, definitely makes a guy wonder how "tested" everything is before it's out the door